Progress has been made in the purification of Beta-galactosidase A and B to homogeneity. We will purify sufficient quantities of these two isozymes to compare them with respect to their subunit structure, carbohydrate composition and aggregation and disaggregation. An assay has been worked out for the measurement of activity of GM2 Beta-D-N-acetylgalacosaminidase in cultured fibroblasts from normal individuals. We are now set to examine the nature of the mutation using this substrate in unusual variants involving hexosaminidase A deficiency in humans. These studies will be carried out over the next several years using cultured skin fibroblasts. Several unusual mutants which resemble Beta-galactosidase deficient states have been collected. However, assays of activity indicate no deficiency of this enzyme. Several have been identified as having significant glycopeptide excretion. These glycopeptide excretion products will be purified and structurally characterized in order to backtrack to find the deficient enzyme in these patients. BIBLIOGRAPHIC REFERENCES: Human Leukocyte Peroxidase: Activity of a Soluble and Membrane-Bound Enzyme Form in Normal Persons and Patients with Neuronal Ceroid-lipofuscinosis. H. Pilz, J.S. O'Brien and R. Heipertz. Metabolism, Vol. 25, No. 5:561-569, 1976. Ganglioside GM2 N-acetyl-beta-D-galactosaminidase and asialo GM2 (GA2) N-acetyl-Beta-D-galactosaminidase: studies in human skin fibroblasts. John S. O'Brien, Anthony G.W. Norden, Arnold L. Miller, Russell G. Frost and Thaddeus E. Kelly. Clin. Genet. 11:171-183, 1977.